From: Science Digest, July 1982, p. 18

	[Figure caption: This common-looking kangaroo is actually a member
of a totally new species found in Hawaii. Scientists think rapid
evolution may explain the creatures' emergence.]

	INSTANT EVOLUTION

	What's stranger than finding a colony of kangaroos on a Hawaiian
island? Finding that the colony is an entirely new species only 60
generations old.

	This intriguing suggestion is offered by James Lazell, Jr., a
continent-hopping field biologist whose specialty is observing rare
animals. Lazell recently spent time on Oahu, trailing the island's only
known species of kangaroo, the Kalihi rock wallaby.

	How the wallaby population got to Hawaii in the first place is well
known. The animals are all descendants of a single pair of Australian
wallabies that fled from a Hawaiian zoo in 1916. Capable of reproducing
at about a year old, the wallabies are now estimated to have grown to
several hundred in number.

	The big mystery is why the Hawaiian wallabies are so different in
color and size from their Australian ancestors. Lazell comments: "At
first I suspected we were dealing with a form that had simply
disappeared from Australia some time after the ancestral pair had been
shipped to Hawaii. But when I went to Australia and checked all the
historically documented specimens, nothing matched."

	Lazell offers two possible explanations. The first, he notes, is
known as a "founder effect." Since the entire island population
descended from the same pair, any genetic eccentricity appearing in the
common ancestors would be uniformly transmitted to succeeding
generations. On the other hand, the creatures' physiology might simply
be the result of remarkably rapid evolution. Those wallabies who were
smaller and lighter in color -- thus better suited to the Hawaiian
environment -- would have a better chance at survival and reproduction.

	If the latter is the case, the wallabies' adaptation to their new
environment was not only swift but extraordinarily thorough. Lazell
reports that not only did the animals' external appearance change, so
did the amino acid structure of at least one of their liver enzymes,
which would have helped them safely feed on otherwise toxic plants on
Oahu.

	The question remains: how did the wallabies evolve in what amounts
to a mere eyeblink in time? Lazell is still uncertain. Scientists have
observed similar phenomena before, but even in those instances, it took
several centuries for marked evolutionary changes to occur. The Oahu
kangaroos make even that pace seem leisurely. Says Lazell, "To evolve
into an entirely new species in only sixty generations... that's pretty
spectacular."